An attractive hairstyle is nowadays generally regarded as an indispensable part of a well-groomed appearance. In order to achieve such an attractive hairstyle, the hair is subjected to cosmetic treatment methods ranging from cleaning by means of a shampoo to permanent shaping by means of chemical/thermal processes or permanent oxidative color lightening. For oxidative color lightening (bleaching) of the hair, use is made of aqueous oxidant preparations. These preparations can be prepared by the consumer for example in situ by mixing the required components. One point that is essential for consumer safety with this type of application method is the avoidance of product dust, in particular dust from oxidant-containing precursors.
First approaches to solving the above-described technical problems can be found in the literature. For instance, German patent application DE 19613941 A1 describes a method for producing powdered bleaching agents which do not generate dust. The bleaching agents include at least one peroxide compound, which is mixed with suitable thickeners and then packaged in portions in water-soluble pouches for transport and further processing.
The use of spraying methods for applying oxidative preparations is relatively uncommon in hair cosmetics.
The spraying systems used in hair cosmetics include in particular pump sprays or aerosol sprays, by means of which the cosmetic preparations are sprayed via a valve either by means of mechanical forces or with the aid of a propellant. Both methods have obvious disadvantages. While pump sprays are generally not suitable for a sustained and even spray application of cosmetic hair preparations, aerosol sprays are based on the use of propellants or propellant gases, which on the one hand have no cosmetic effect and on the other hand can pose a risk to consumers if not handled correctly.
Against this background, there is a need for alternative ways of atomizing cosmetic hair preparations. Flash evaporation has proven to be advantageous as one such alternative spraying method. In this method, which is described for example in international patent application WO 200183071 A1 (Henkel), a liquid or paste-like solvent-containing composition is heated in a closed chamber to a temperature above the boiling point of the solvent, thereby generating an overpressure in the composition. When the pressure is released (throttled), the liquid evaporates and can then be atomized for example by means of a suitable nozzle.
Therefore, although flash evaporation is suitable in principle for the spray application of cosmetic hair preparations, at the same time it is not possible to atomize every cosmetic hair preparation by means of a flash evaporation method. This is due on the one hand to the heating of the cosmetic preparation that is necessary for the flash evaporation, and on the other hand to the specifics of the spray mist produced by flash evaporation, for example the droplet size and droplet density produced in the spray mist.
The problem addressed by the present invention is therefore that of providing specific cosmetic hair preparations for the oxidative treatment of keratinous fibers, which on account of their chemical and physical properties are suitable for targeted spray application by means of a flash evaporation device. The preparations are also intended to be suitable for achieving a good cosmetic effect after application by means of a flash evaporation method. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with this background of the invention.